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Question : 94 of 100
Marks:
+1,
-0
Solution:
Given,
9n−8n−1=64α⇒α=‌=‌| (‌nC0⋅1+‌nC1⋅81+‌nC2⋅82+......+‌nCn⋅8n)−8n−1 |
| 82 |
=‌| 1+8n+‌nC2⋅82+....+‌nCn⋅8n−8n−1 |
| 82 |
=‌| ‌nC2⋅82+‌nC3⋅83+....+‌nCn⋅8n |
| 82 |
=‌nC2+‌nC3⋅8+‌nC4⋅82+...‌nCn⋅8n−2Also given,
6n−5n−1=25β⇒β=‌=‌| ‌nC0⋅1+‌nC1⋅5+‌nC2⋅52+.....+‌nCn⋅5n−5n−1 |
| 52 |
=‌| 1+5n+‌nC2⋅52+‌nC3⋅53+....+‌nCn⋅52−5n−1 |
| 52 |
=‌| ‌nC2⋅52+‌nC3⋅53+‌nC4⋅54+....+‌nCn⋅5n |
| 52 |
=‌nC2+‌nC3⋅5+‌nC4⋅52+.......+‌nCn⋅5n−2 ∴α−β=(‌nC2+‌nC3⋅8+‌nC4⋅82+....+‌nCn⋅8n−2)−(‌nC2+‌nC3⋅5+‌nC4⋅52+...+‌nCn⋅5n−2.=‌nC3⋅(8−5)+‌nC4⋅(82−52)+...+‌nCn(8n−2−5n−2)
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